SPIROMETER UNIT. 



45 



FIG. 17. Specimen kymograph records 

 made in the calibration of the ventila- 

 tion adder. 



The upper portion shows the record made 

 with a stroke of 556 c.c. and the lower 

 with a stroke of 150 c.c. The complete 

 revolutions of the ventilation adder wheel 

 are recorded by the signal magnet in the 

 horizontal line below each kymograph 

 record. 



The record on the kymograph drum 

 made in the two calibrations is shown 

 in figure 17. When a rubber band is 

 placed around the pawl, the back-lash 

 is increased, but the use of this rubber 

 band is found desirable, as the sound 

 of the metal pawl striking against the 

 corrugations of the wheel attracts the 

 attention of the subject and makes 

 him conscious of his respiration. 



Kymograph records. It is the gen- 

 eral custom in this laboratory to 

 smoke the kymograph records heavily, 

 so as to give a sharp contrast and to 

 enable us to reproduce them in whole 

 or in part by using the original record 

 as a negative. The greatest care is 

 taken to keep the curves from acci- 

 dental abrasion, and to arrange the 

 recording devices so that there need 

 be little alteration in reproducing the 

 record for publication. An effort is 

 made to adjust the speed of the kymo- 

 graph to a uniform rate, so that the experimental records may all be 

 comparable. 



GENERAL ROUTINE OF AN EXPERIMENT. 



The general routine of a respiration experiment with this apparatus 

 is practically the same as with the tension-equalizer unit. There are, 

 however, some additional manipulations required, owing to the increase 

 in number of observations. The subject, after securing a comfortable 

 position, is attached to the apparatus by means of either the mouth- 

 piece or nosepieces. Before the experiment is actually begun, the 

 carbon-dioxide absorbers are weighed and the meter reading or the 

 weight of the oxygen cylinder is obtained. The spirometer level is set 

 at such a height (as indicated by a millimeter scale) that there will be 

 no danger of all the air being drawn out of the spirometer bell by the 

 subject in a deep inspiration. The contact of the ventilation adder is 

 set at zero and the kymograph is adjusted so that the time marker, the 

 revolution counter, and the pointer of the spirometer bell will write 

 freely. The height of the spirometer bell may be read either while 

 the apparatus is running or before the ventilation has been started. 

 Of course it is necessary to use the same method of reading at the end 

 of the experiment as at the beginning. Everything being in readiness, 

 and the air of the apparatus circulating, the three-way valve is then 



